Waves in a Uniform Warm Magnetoplasma

Abstract

So far we have ignored the effect of the plasma pressure on wave propa­gation. This was equivalent to assuming that the wave speed was much greater than the thermal speed of the particles. In the magnetosphere there is a wide variety of populations of energetic particles, often far from thermal equilibrium. These particles can give rise to new forms of wave as well as modifying those already studied. If they are far from thermal equilibrium they can provide a source of free energy for wave generation or amplification. It is therefore seldom appropriate to treat the particles as if they constituted a gas in thermal equilibrium, characterized by a scalar pressure, a uniform temperature and a simple equation of state. Nevertheless this is what we shall do in this chapter. Our excuse is that this gives us a physical intuition for the kind of effects that can be intro­duced; when we use a more complicated kinetic or quasi-linear approach we shall have a better appreciation of the results we obtain. The sim­ple picture may guide us to look for appropriate solutions to the more complicated problems.